In some ways a milestone is just a rock. In other ways it signifies the end of one thing and the beginning of something new. A couple of milestones this week:
The end of "I can't afford a computer:" Wal-Mart 
and Everex are offering a reasonably capable desktop PC for a breakthrough regular price of $199, which is less than the price of one night in a New York hotel room. It's not one of those "we only have two at that price" deals; it's available online and at many retail stores starting tomorrow. Look for this to further screw up conventional tech retailers, as Wal-Mart's flat-screen TV maneuver did last year.
The Google desktop: The aforementioned Everex runs a special Google-centric desktop on a Linux kernel. It's probably not the same one that's been rumored for awhile, but it demonstrates that Netscape's 1997 "Webtop" vision was right, after all. Bad news for Microsoft, which is so last century.
The coming Google hegemony: The aforementioned search giant is now the fifth largest company in the United States in terms of market value, closing in on AT&T. Unlike the bogus valuations being attributed to Facebook, this one is real.
The network of social networks: Google, hi5, Friendster, LinkedIn, Viadeo, Ning, Salesforce and Oracle are announcing tomorrow a set of open interfaces for programming "social networking" tools that talk to one another. The walls around the garden just got a lot lower.